Method and device for estimating a velocity of an object

Abstract

A method is provided for estimating a velocity of an object located in the environment of a vehicle. Detections of a range, an azimuth angle and a range rate of the object are acquired for at least two different points in time via a sensor. A cost function is generated which depends on a first source and a second source. The first source is based on a range rate velocity profile which depends on the range rate and the azimuth angle, and the first source depends on an estimated accuracy for the first source. The second source is based on a position difference which depends on the range and the azimuth angle for the at least two different points in time, and the second source depends on an estimated accuracy for the second source. By minimizing the cost function, a velocity estimate is determined for the object.

What is claimed is: 
     
       1. A method comprising:
 acquiring, via a sensor, detections of a range, an azimuth angle, and a range rate of an object in an environment of a vehicle for at least two different points in time; 
 via a processing unit:
 generating a cost function that depends on a first source and a second source, the first source based on a range rate velocity profile that depends on the rate range and the azimuth angle and the first source depends on an estimated accuracy for the first source, the second source based on a position difference that depends on the range and the azimuth angle for the at least two different points in time and the second source depends on an estimated accuracy for the second source; and 
 determining a velocity estimate for the object by minimizing the cost function, 
 
 wherein
 a plurality of detections of the range, the azimuth angle, and the range rate are acquired for the object for each of the at least two points in time; 
 a respective standard deviation is estimated for the range, the azimuth angle, and the range rate based on the plurality of detections; and 
 the first source and the second source are based on a normalized estimation error squared (NEES) that includes the respective standard deviations of the range, the azimuth angle, and the range rate. 
 
 
     
     
       2. The method of  claim 1 , wherein:
 the range rate velocity profile depends on the plurality of detections of the rate range and the azimuth angle; 
 the position difference depends on the plurality of detections of the range and the azimuth angle for the at least two different points in time; 
 the estimated accuracy of the first source depends on the standard deviation of the range rate and the standard deviation of the azimuth angle; and 
 the estimated accuracy of the second source depends on the standard deviation of the range and the standard deviation of the azimuth angle. 
 
     
     
       3. The method of  claim 2 , wherein:
 different standard deviations of the range, the azimuth angle, and the range rate are estimated for at least one of:
 each of the at least two points in time; or 
 each detection of the range, the azimuth angle, and the range rate. 
 
 
     
     
       4. The method of  claim 2 , wherein:
 the cost function comprises a first contribution based on a normalized estimation error squared (NEES) related to the first source and a second contribution based on a normalized estimation error squared (NEES) related to the second source. 
 
     
     
       5. The method of  claim 4 , wherein:
 the first contribution and the second contribution each comprise a sum of elements over the plurality of detections and each element is estimated as a normalized estimation error squared (NEES) for the respective detection. 
 
     
     
       6. The method of  claim 5 , wherein:
 the elements of the first contribution are based on a range rate equation and on the standard deviation of the range rate. 
 
     
     
       7. The method of  claim 5 , wherein:
 the elements of the second contribution are based on:
 the position difference for the respective detection, 
 a velocity covariance matrix estimated based on the standard deviations of the range and the azimuth angle, and 
 a time interval between the at least two different points in time for which the range and the azimuth angle are acquired by the sensor. 
 
 
     
     
       8. The method of  claim 5 , wherein:
 the cost function is generated as an average of the first contribution and the second contribution. 
 
     
     
       9. The method of  claim 1 , wherein:
 a component of the velocity is estimated by setting a derivative of the cost function with respect to a velocity component to zero. 
 
     
     
       10. The method of  claim 1 , wherein
 the cost function and the velocity estimate are determined by assuming a constant velocity of the object ( 23 ) in order to initialize a Kalman filter state estimation of the velocity. 
 
     
     
       11. A device comprising:
 a sensor configured to provide data for acquiring detections of a range, an azimuth angle, and a range rate of an object in a field of view of the sensor for at least two different points in time; and 
 a processing unit configured to:
 generate a cost function that depends on a first source and a second source, the first source based on a range rate velocity profile that depends on the range rate and the azimuth angle and the first source depends on an estimated accuracy for the first source, the second source based on a position difference which depends on the range and the azimuth angle for the at least two different points in time and the second source depends on an estimated accuracy for the second source; and 
 determine a velocity estimate for the object by minimizing the cost function, 
 
 wherein the processing unit is further configured to: 
 acquire a plurality of detections of the range, the azimuth angle, and the range rate for the object for each of the at least two points in time; and 
 estimate a respective standard deviation for the range, the azimuth angle, and the range rate based on the plurality of detections; 
 wherein the first source and the second source are based on a normalized estimation error squared (NEES) that includes the respective standard deviations of the range, the azimuth angle, and the range rate. 
 
     
     
       12. The device of  claim 11 , wherein the sensor includes at least one of: a radar sensor or a Lidar sensor. 
     
     
       13. The device of  claim 11 , wherein the device comprises a vehicle. 
     
     
       14. The device of  claim 11 , wherein:
 the range rate velocity profile depends on the plurality of detections of the rate range and the azimuth angle; 
 the position difference depends on the plurality of detections of the range and the azimuth angle for the at least two different points in time; 
 the estimated accuracy of the first source depends on the standard deviation of the range rate and the standard deviation of the azimuth angle; and 
 the estimated accuracy of the second source depends on the standard deviation of the range and the standard deviation of the azimuth angle. 
 
     
     
       15. The device of  claim 11 , wherein:
 the first contribution and the second contribution each comprise a sum of elements over the plurality of detections, wherein each element is estimated as a normalized estimation error squared (NEES) for the respective detection. 
 
     
     
       16. The device of  claim 15 , wherein:
 the elements of the first contribution are based on a range rate equation and on the standard deviation of the range rate. 
 
     
     
       17. The device of  claim 15 , wherein:
 the elements of the second contribution are based on:
 the position difference for the respective detection, 
 a velocity covariance matrix estimated based on the standard deviations of the range and the azimuth angle, and 
 
 a time interval between the at least two different points in time for which the range and the azimuth angle are acquired by the sensor. 
 
     
     
       18. A computer-readable storage media storing computer-readable instructions that, when executed by one or more processors, cause the one or more processors to:
 receive, via a sensor, data for acquiring detections of a range, an azimuth angle, and a range rate of an object in a field of view of the sensor for at least two different points in time; 
 generate a cost function that depends on a first source and a second source, the first source based on a range rate velocity profile that depends on a range rate and the azimuth angle and the first source depends on an estimated accuracy for the first source, the second source based on a position difference which depends on the range and the azimuth angle for the at least two different points in time and the second source depends on an estimated accuracy for the second source; 
 determine a velocity estimate for the object by minimizing the cost function; 
 acquire a plurality of detections of the range, the azimuth angle, and the range rate for the object for each of the at least two points in time; and 
 estimate a respective standard deviation for the range, the azimuth angle, and the range rate based on the plurality of detections; 
 wherein the first source and the second source are based on a normalized estimation error squared (NEES) that includes the respective standard deviations of the range, the azimuth angle, and the range rate.